A multiple phase stepper motor is a rotary motion apparatus having a plurality of windings or phases which provides desired incremental movement of a load in response to sequential input control pulses and will provide the desired movement of that load coupled with the motor in response to the control pulses until the required load torque exceeds the electromagnetic capability of the motor. When this pull-out condition occurs the motor will miss desired step movements, and the torque at which the step movements are missed is a function of the motor speed in relation to steps per second, the basic motor design and the electric drive circuit controlling the stepper motor.
Typical multiple phase stepper motors are presently available in the open market such as, made and sold by Superior Electric Company of Bristol, Conn. Model M112FJ12. A control apparatus, for such a motor is generally used and often includes a programmed microprocessor, operative to sequentially energize the stepper motor stator coils with the required input control pulses to obtain a given angular speed, including accelerating and decelerating below the torque limits of the stepper motor, is well known in the prior art.
It is known in the prior art to provide a motor for opening and closing the passenger doors on a transit vehicle in response to door command signals from a vehicle automatic train operation control apparatus, as described in an article entitled Recent Applications of Microprocessor Technology to People Mover Systems by M. P. McDonald et al. and published in the conference proceedings for the 29th IEEE Vehicle Technology Group Conference held in Chicago, Ill. during March, 1979.